"It's not completely over - we have to get him home - this is a big hurdle done with and it's now just getting him home to his family. He'll feel better then," he added.

Robert Hughes felt bored in hospital and it was "not the best environment to be stuck in 24/7," his brother said. He was diagnosed at Princess Margaret Hospital in Kwai Chung.

The family praised hospital staff and the standard of healthcare. They also thanked the police for the speed in dealing with the case and the handling of the sensitive matter.

"We sought the Department of Justice's advice, and the British man was released," a police spokeswoman said.

Robert Hughes' mother Helen plans to escort her son back to Liverpool from Hong Kong but is searching for a new one-way flight after Virgin Atlantic banned the young man. Hughes had worked as an English teacher on the mainland.

Dr Edmond Chan Lap-kei, a specialist psychiatrist and a Hong Kong Mental Health Association representative, said life or study stresses are just two factors that can trigger schizophrenia.

He also said the illness is normally found in people who have an underlying, possibly undiagnosed condition.

"The most common symptoms of schizophrenia are hallucination, hearing non-existing voices, and delusions or the sufferer … believing they are being persecuted though it is not true," Dr Chan said.

A survey in 2012 conducted by city psychiatrists suggested one-third of Hongkongers suffered from a mental illness.

The decision to take Robert Hughes home was not an easy one, Peter Hughes said. "I really didn't want to take him back home because he lives, works and enjoys China, but he was acting so strangely, he seemed to be confused and didn't know where he was."

Hughes said his brother did not remember anything that happened on the plane. "He says he 'must have done something but I don't know what', and it must be frustrating for him."